Reversible electromagnetic fluid pump



July 21, 1964 H. HEYMAN 3,141,413

REVERSIBLE ELECTROMAGNETIC FLUID PUMP Filed June 26, 1963 2 Sheets-Sheet 1 INVENTOR. Henry Heyman BY Maw July 21, 1964 H. HEYMAN REVERSIBLE ELECTROMAGNETIC FLUID PUMP 2 Sheets-Sheet 2 Filed June 26, 1963 Fig. 4

" INVENTOR.

5 BY Henry Hey/nan %M/QW United States Patent 3,141,413 REVERSIBLE ELECTROMAGNETIC FLUID PUMP Henry Heyman, Santa Fe, N. Mex., assignor to the United States of America as represented by the United States Atomic Energy Commission Filed June 26, 1963, Ser. No. 290,871 3 Claims. ((21. 1031) This invention relates to electromagnetic fluid pumps in which an electrically conducting fluid is impelled along a channel by the force which results from the reaction between an electric current passing through the fluid and an impressed magnetic field.

In general, the electromagnetic fluid pump is old in the art and is shown, for example, in Patent 2,397,785 to Freidlander, and in Patent 1,298,664 to Chubb.

The electromagnetic fluid pump has hitherto failed to find extensive application in the pumping art for the reason that an absolute necessity for its use was lacking. However, the advent of the nuclear reactor, wherein molten metallic coolants or coolants containing radioactive substances are utilized, has changed the use-picture of this type of pump drastically so that this type pump is presently indispensable for the purpose.

An essential feature of the electromagnetic fluid pump is the necessary diametrically opposite connections to the coolant duct. Inasmuch as the coolant duct is fabricated of metal, such as stainless steel, and the path through the coolant, which may be molten sodium, is short, the resistance through the coolant and the duct material is generally only a small fraction of an ohm. Consequently, the exercise of close control over the quantity of coolant propelled by the pump requires a power supply capable of close voltage control, generally in the range of between 0.25 and 1.0 volt, with an output capacity ranging up to 500 amperes or more. Power supplies are expensive and it is, therefore, desirable that only one power supply be used for both field excitation and the cross connection through the duct. This may be accomplished by the series-connecting of the field electromagnet excitation coil or coils with the terminals on the duct. The electromagnetic coils are of heavy construction to sustain currents in the range of 500 amperes and are provided with appropriately heavy, substantially inflexible terminal lugs.

It is an essential feature of a circulating pump in a metallic coolant loop, such as utilize liquid sodium, for example, to be able to reverse the direction of the pumping action in order, for example, to remove deposits of metallic oxide in the duct. It is apparent that this cannot be done in a series-connected electrical system by merely reversing the connections from the power supply to the input terminals of the series circuit. It is also not feasible to provide insulated flexible jumpers for the reason that the space around such pumps is very limited due to the heavy lagging on the coolant ducts and other proximate apparatus. Furthermore, the stresses and strains on the fluid duct terminals which would be unavoidable during connecting and disconnecting cumbersome jumpers having no fixed spatial position would result in the ultimate breakage of the duct terminals and a consequent exceedingly expensive and inconvenient interference with 3,141,413 Patented July 21, 1964 ice The foregoing objective is attained in brief by utilizing two adjacent ribbon wound pancake coils having oppositely directed windings so that the inner ends of the windings are connected together and the end terminals are on the outside turn of the coils, supporting the coils on a cylindrical pole piece which is centered over the coolant duct crosscurrent path, so that the coils can be rotated through an arc, providing conducting arms on the coolant duct so that the low outside coil terminal can be selectively connected to one or the other of the coolant arms, and the excitation current source feed lines can be connected to the other of the fluid duct conducting arms and the terminal on the upper coil. Other features of this invention include terminal configurations such that little, if any, flexing of feed lines or other conductors is necessary in reversing the fluid duct cross current path to obtain fluid propulsion reversal.

Other objectives and advantages of the present invention will become apparent from the remainder of this specification which includes the drawings.

In the drawings:

FIGURE 1 is a schematic showing of an electromagnetic fluid pump,

FIGURE 2 is a perspective view of the pump of the present invention with excitation coils removed,

FIGURE 3 is a fragmentary view of the fluid duct with welded-on electrical terminals,

FIGURE 4 is a perspective exploded view of the excitation coils of the present invention, and

FIGURE 5 is a cross-sectional view on plane 5-5 of FIGURE 2.

Referring to the drawings, FIGURE 1 shows an electromagnetic fluid pump in simple schematic form comprising a fluid duct 11 and a magnetic circuit 13. The fluid duct 11 is shown in cross section. The duct is of metal, preferably stainless steel, and is flattened to oval shape to provide a longer electrical current path through the fluid and to reduce the reluctance of the magnetic path. A pair of electrical terminals 15 and 17 are affixed to the tube to permit the application of a cross current through the fluid which will be contained therein. The magnetic circuit 13 of the pump comprises a complete magnetic yoke, including a pair of pole pieces 19 and 21, which bridge the coolant duct transversely of the cross-current path.

The pole pieces insulatingly bridge the coolant tube, preferably symmetrically, about the median line of the terminals. The interaction of the transverse magnetic field and the cross current in the fluid results in propulsion of the fluid in the usual manner. In order to reverse the direction of propulsion, only one or the other of the direction of the magnetic field or the direction of cross current may be reversed.

In order to understand the present invention, it is necessary to appreciate the rigidity and massiveness of the electrical conductors utilized. For example, to properly propel the coolant through a tube having a diameter in the range of one-half inch, a pair of coils, each having five to seven turns of ribbon conductor, of dimension one-eighth inch by one inch, are utilized. Such pumps are operated under conditions of abnormal temperature, such as 600 to 700 degrees C. At these temperatures copper is not an entirely satisfactory conductor because of oxidation problems and, as a result, silver is the preferred conductor. It is apparent that terminals consisting of silver strap of the dimensions given are rigid and not adaptable to bending at will to expedite connection transfer. Neither is it convenient to use flexible electrical jumper connections for the purpose of making changes in polarity of electrical connections in these devices under conditions of use because of the massiveness and cumbersome nature of jumpers of suitable cross 6 section. In addition, the high temperature of the environment mitigates against the utilization of any type of insulated jumper connection because of the lack of endurance of insulation under these conditions.

The coils are wound with interleaved mica sheet between the adjacent surfaces in the winding, and are insulated from one another by a sheet of mica insulation. The top coil is wound in a spiral which is opposite in direction from the spiral direction of the bottom coil. The coils are assembled in close proximity with each other and are rigidly secured together by a substantial cross bar welded, silver-soldered or brazed in place to provide good electrical connection. FIGURE 4 shows the details of the connection.

Referring to FIGURE 2, it is seen that the coolant tube 11 is provided with strap-like terminals 15 and 17 welded thereto as shown in FIGURE 3. Terminal 15 extends radially outward from the coolant duct and is connected to an elongated connector arm 23 extending substantially parallel to the fluid duct. Terminal member 23 is provided with terminal clamping means 25 which may be simply a bolt-receiving aperture, but which is preferably an anchored clamping bolt as shown. Outwardly of clamping bolt 25, the terminal conductor is deformed into a downward direction so that a final elongated arm 28 passes substantially transversely under the coolant duct to provide a second terminal in its end portion.

Terminal 17 is likewise integral with an arm 27, which is normal thereto, and which extends parallel to the duct in the same direction as previously described arm 23. Terminal arm 27 is similarly provided with terminal-connecting means which may be a clamping bolt 29. Terminal clamps 25 and 29 are on radii equidistant from a center point on the coolant duct between terminals 15 and 17. Terminal arm 27 outwardly of terminal-connecting clamp bolt 29 is provided with a doWnturned terminal car 31, provided with terminal-connecting means, such as clamping bolt 33.

Magnetic yoke 13 is provided with an elongated cylindrical pole piece 19 and an opposing short pole piece 21. The ends of pole pieces 19 and 21 closely engage the coolant duct with intervening mica sheets between terminal arms 15 and 17 and are centrally positioned over the aforementioned center point of the duct between the terminal arms. Elongated pole piece 19 is of a length slightly greater than the thickness of the desired number of excitation coils plus the length of the clamping bolts 25, 29.

Referring to FIGURE 4, the configuration of the two excitation coils 35, 37 which are utilized in the present embodiment are shown. These coils are fabricated, as described supra, of about five turns of silver strap having a cross section of one-eighth inch by 1 inch. The open center of the coil is cylindrical and has a diameter somewhat larger than 1.25 inches to accommodate a sleeve of insulation and the one square inch in cross section cylindrical pole piece 19. It has been found that iron of the type AISI No. C1019 is satisfactory for operation for the present purpose. The magnet coils are of the ribbon-wound pancake type and are wound with mica sheet between Winds for insulation purposes, as shown in FIGURES 4 and 5. As shown, the upper coil, identified by numeral 35, is wound counterclockwise from the outside in. Lower coil 37 is wound clockwise from the outside in. A cross bar 38 of flat strap of electrical conductor of a cross section similar to that utilized for the coils themselves is attached, as by silver soldering, brazing or welding, to the end of the innermost turn of each coil.

The technique for reversal of pump action is to rotate the coils as a unit to certain alternate connections which results in reversal of the current through the coolant duct. By the use of opposite winding directions in the two coils continuity is established by connectingstrap 38 without disturbing the shape of the cylindrical center hole of the Coils y j ct nable extent. This scheme also it'll,

avoids the necessity for bringing out connections from the inside ends of the coils along the lateral surfaces thereof, which would be awkward to insulate and susceptible to breakage. Strap 38, furthermore, is sufficiently rigid as to combine both windings into one rigid assembly, no other cross structure being necessary. Coils 35 and 37 are preferably positioned axially adjacent one another with just a layer of mica insulation in between. Coil 35 is provided with an outside terminal having arcuately-spaced connecting points subtending an angle of approximately but which, in any case, is equal to the angle subtended by terminal connections 25 and 29 on fluid tube terminals 15 and 17. Coil 37 is provided with an outwardly extending terminal strap, indicated by numeral 53, which extends outwardly on a radius equal to the radius of terminal-connecting points 25 and 29 on fluid tube terminals 15 and 17, respectively.

Coils 35 and 37 are rotatably supported as a unit on pole piece 19. To this end, pole piece 19 is provided with an enlarged foot piece 20 to support the coils.

Referring to FIGURES 2 and 4, when the coils are in position on pole piece 19 for one selected direction of fluid propulsion terminal strap 53 of coil 37 overlays terminal arm 23 of fluid tube terminal 15 and the clamping bolt 25 passes through terminal aperture 26, so that when the nut 30 is tightened, coil terminal 53 and tube terminal 15 are electrically connected. At this time feed bus 61 will be secured to the most counterclockwise terminal 36 of coil 35 by a clamping bolt 32 af'fixed to the feed bus and passing through aperture 37. The second feed bus 71 (see FIGURE 5) will be clamped as by bolt means to terminal arm 27 of coolant tube terminal 17. It is now seen that if feed bus 61 is connected to the positive terminal of a current source that the ampere turns of the upper coil are counterclockwise and the ampere turns of coil 37 are likewise counterclockwise. The cross current through terminals 15 and 17 and the coolant duct is from left to right. Consequently, fluid in the tube is propelled from right to left along tube 11 in FIGURE 2. If it is desired to reverse the direction of coolant propulsion, it is only necessary to loosen three bolts, i.e., detach feed bus 61 from counterclockwise terminal 36 of coil 35, detach lower coil terminal end 53 from arm 23 of tube terminal 19 and detach feed bus 71 from terminal end 31 of tube terminal 17. The set of coils is now raised on the pole piece to clear the clamp bolts and are rotated so that the terminal end of connector 53 overlies arm 27 and lowered in place with apertures 37 and 26 over the corresponding terminal clamp-bolts. Feed bus 61 is now attached to clockwise terminal arm 36 of upper coil 35 and feed bus 71 is now clamped to terminal arm 28 of tube terminal 15. It is now seen that the ampere turns of the coil have not been changed but that the cross current through the fluid duct has been reversed, passing from right to left, thereby resulting in the left to right direction of fluid propulsion in tube 11.

From the foregoing it is seen that an electromagnetictype fluid pump is disclosed having novel features which permit the expeditious switching of connections necessary to obtain a reversal in direction of pumping action. In brief, the salient features are the arcuately-spaced terminals on the fluid duct, the unitary assembly of reversewound coils supported on a cylindrical pole piece and radial terminals on the exterior of the coils to enable current switching through the fluid duct by simply rotating the coil through an arc. The invention has been described with reference to a specific embodiment, but many modifications may be made Without departing from the spirit of the invention. For example, the shape of the fluid duct terminals need not be as shown, but may diverge on less than a straight angle so long as the connecting points are on an are centered on the axis of the pole piece. The coils may be wound of hollow ribbon connected by a hollow cross bar so that coolant can be introduced through the terminals or any accessible point on the outer terminal ends. Accordingly, it is intended that the invention be considered to be limited only by the appended claims interpreted in the light of the prior art.

What is claimed is:

1. An electromagnetic fluid pump for circulating electrically conductive coolant comprising a fluid duct, a pair of oppositely disposed transverse terminals integral with a portion of said duct, connecting means on said terminals located on an arc with respect to a center point of the duct between the said transverse terminals, a magnetic yoke supported with its pole pieces centrally located and bridging the duct portion between the transverse terminals, said magnetic yoke having an elongated cylindrical pole piece, a pair of excitation coils, reverse wound with respect to each other, rotatably supported on said cylindrical pole piece, means interconnecting the inner ends of said coils, a radial terminal member on the outer end of the lower coil having connecting means located adjacent to the plane of and on the arc of the said transverse terminal-connecting means, terminal extension portions integral with each of said transverse terminals and having end portions having planar surfaces in proximate opposition, a terminal element affixed to the outer turn of the upper coil and having two terminal-connecting portions on an arc centered on the axis of the pole piece, said terminalconnecting portions circumscribing an are equal to the arc circumscribed by the fluid duct transverse terminal-connecting means, one of a pair of electrical power feed lines having an end terminal portion disposed between the fluid duct terminal extension portions, and the other of the electrical feed lines having an end disposed adjacent in overlapping relation to the upper coil terminal element, whereby reversal of the current path only through the duct is obtained by disconnecting adjacent terminals, rotating the coils to the alternate connecting position and reconnecting the adjacent terminals.

2. The device of claim 1 in which said excitation coils are ribbon-conductor wound in a spiral with one coil having a right-hand spiral and the other coil having a lefthand spiral, a flat ribbon-like conductor edgewise afiixed to the inner end extremity of each of said coils to interconnect them electrically and mechanically and without reducing the coils center opening.

3. The device of claim 2 in which the elongated pole piece is provided with an end portion having a cross section in excess of the excitation coils open centers, whereby said coils are rotatably supported on said pole piece.

No references cited. 

1. AN ELECTROMAGNETIC FLUID PUMP FOR CIRCULATING ELECTRICALLY CONDUCTIVE COOLANT COMPRISING A FLUID DUCT, A PAIR OF OPOOSITELY DISPOSED TRANSVERSE TERMINALS INTEGRAL WITH A PORTION OF SAID DUCT, CONNECTING MEANS ON SAID TERMINALS LOCATED ON AN ARC WITH RESPECT TO A CENTER POINT OF THE DUCT BETWEEN THE SAID TRANSVERSE TERMINALS, A MAGNETIC YOKE SUPPORTED WITH ITS POLE PIECES CENTRALLY LOCATED AND BRIDGING THE DUCT PORTION BETWEEN THE TRANSVERSE TERMINALS, SAID MAGNETIC YOKE HAVING AN ELONGATED CYLINDRICAL POLE PIECE, A PAIR OF EXCITATION COILS, REVERSE WOUND WITH RESPECT TO EACH OTHER, ROTATABLY SUPPORTED ON SAID CYLINDRICAL POLE PIECE, MEANS INTERCONNECTING THE INNER ENDS OF SAID COILS, A RADIAL TERMINAL MEMBER ON THE OUTER END OF THE LOWER COIL HAVING CONNECTING MEANS LOCATED ADJACENT SAID COILS, A RADIAL TERMINAL MEMBER ON THE OUTER END OF THE LOWER COIL HAVING CONNECTING MEANS LOCATED ADJACENT TO THE PLANE OF AND ON THE ARC OF THE SAID TRANSVERSE TERMINAL-CONNECTING MEANS, TERMINAL EXTENSION PORTIONS INTEGRAL WITH EACH OF SAID TRANSVERSE TERMINALS AND HAVING END PORTIONS HAVING PLANAR SURFACES IN PROXIMATE OPPOSITION, A TERMINAL ELEMENT AFFIXED TO THE OUTER TURN OF THE UPPER COIL AND HAVING TWO TERMINAL-CONNECTING PORTIONS ON AN ARC CENTERED ON THE AXIS OF THE POLE PIECE, SAID TERMINALCONNECTING PORTIONS CIRCUMSCRIBING AN ARC EQUAL TO THE ARC CIRCUMSCRIBED BY THE FLUID DUCT TRANSVERSE TERMINAL-CONNECTING MEANS, ONE OF A PAIR OF ELECTRICAL POWER FEED LINES HAVING AN END TERMINAL PORTION DISPOSED BETWEEN THE FLUID DUCT TERMINAL EXTENSION PORTIONS, AND THE OTHER OF THE ELECTRICAL FEED LINES HAVING AN END DISPOSED ADJACENT IN OVERLAPPING RELATION TO THE UPPER COIL TERMINAL ELEMENT, WHEREBY REVERSAL OF THE CURRENT PATH ONLY THROUGH THE DUCT IS OBTAINED BY DISCONNECTING ADJACENT TERMINALS, ROTATING THE COILS TO THE ALTERNATE CONNECTING POSITION AND RECONNECTING THE ADJACENT TERMINALS. 